1. Field of the Invention
The present invention relates to an art of adhering a thin film and particularly relates to a more effective art in which a thin film whose length corresponds to that of a base plate, is adhered to the thin film adhering side of the plate.
2. Background
In a conventional process of manufacturing a printed circuit board for an electronic appliance such as a computer a laminated film is adhered to the surface of a base plate for a printed circuit. The laminated film consists of a photosensitive resin layer and a light-transmissive resin film. The photosensitive resin layer is adhered directly to the surface of the base plate. The light-transmissible resin film is provided on the photosensitive resin layer to protect it. The laminated film is adhered to the base plate by a thin film adhering apparatus as described in the Japanese Patent Application (OPI) No. 11787/88 (the term "OPI" as used herein means an "unexamined published application") made by the present Applicant.
The procedure of adhering the laminated film to the base plate is as follows. The leading edge portion of the base plate is first conveyed to a thin film adhering position by a base plate conveyance mechanism and stopped in that position. The leading edge portion of the continuous laminated film supplied from a thin film feed roller is then suctioned against a main vacuum suction plate which is a thin film feed member. A thin film temporary adhering member is provided at the leading end of the main vacuum suction plate facing the thin film adhering position so that the leading edge portion of the laminated film is suctioned onto the temporary adhering member. The temporary adhering member has suction holes communicating with a vacuum suction system for suctioning the laminated film. A heater for temporarily adhering the leading edge portion of the laminated film is provided in the temporary adhering member.
The main vacuum suction plate and the thin film temporary adhering member are moved to the vicinity of the thin film adhering position or the surface of the leading edge portion of the base plate. The leading edge portion of the laminated film is then brought into contact with the surface of the leading edge portion of the base plate, and temporarily adhered thereto under heat and pressure by the temporary adhering member. Thereafter the main vacuum suction plate and the thin film temporary adhering member no longer apply suction and are moved away from the thin film adhering position. At that time, the leading edge portion of the laminated film does not deviate from the thin film adhering position because the leading edge portion is already temporarily adhered to the surface of the base plate. A heat and pressure adhering roller is thereafter moved to the thin film adhering position so that the temporarily adhered portion of the laminated film is pressed by the roller. The roller is then rotated as the laminated film remains pressed by the roller so that the whole laminated film is gradually adhered to the surface of the base plate, under heat and pressure, while the base plate is being conveyed.
The laminated film is automatically supplied to the thin film adhering position by the rotation of the heat and pressure adhering roller and the conveyance of the base plate. During the heat and pressure adhering of the laminated film of the surface of a base plate the trailing edge of the base plate is detected to generate a detection signal, in accordance with which the continuous laminated film is cut at the trailing edge portion thereof. For that reason, the length of the cut-off laminated film corresponds to that of the base plate extending in the direction of the conveyance thereof. Cutting the laminated film is performed by moving a disk-shaped cutting member across the direction of the supply of the laminated film as the film is held at the trailing edge portion thereof by the suction of an auxiliary vacuum suction plate provided at the feed passage for the laminated film. The trailing edge portion of the laminated film cut as mentioned above is held by the suction of a thin film trailing edge portion suction member so that an appropriate tensile force is applied to the laminated film. Simultaneously, the trailing edge portion of the laminated film is guided to the trailing edge portion of the base plate so that the trailing edge portion of the film is adhered to the surface of the trailing edge portion of the base plate under heat and pressure, by the heat and pressure adhering roller. The base plate with the laminated film adhered thereto by the thin film adhering apparatus as described above is conveyed to an exposure apparatus installed next thereto. Such a thin film adhering art, in which a portion of a laminated film is temporarily adhered to a base plate for a printed circuit and the laminated film is thereafter completely adhered to the base plate, under heat and pressure, was disclosed in the West German Patent DE No. 3334009 C2 and the Japanese Patent Application No. 49169/87.
The above-mentioned conventional procedure of adhering the laminated film to the base plate includes the step of temporarily adhering the leading edge portion of the laminated film to the base plate. For the temporary adhering complicated conditions such as temporary adhering temperature, temporary adhering period and temporary adhering pressure need to be set. This is a problem. For example, some laminated bodies cannot necessarily be securely adhered to the base plate. For such reasons, the temporary adhering conditions are complicated. The conditions are likely to vary due to the number of times of temporary adherence, the change in the environment and so forth. This is another problem. If the photosensitive resin layer of the laminated film is nonuniformly adhered to the base plate or the base plate is so thin as to be likely to be affected by the heat, a void is caused as a defect between the temporarily adhered portions of the film and the plate such that the film may not remain adhered to the plate. This is yet another problem. The leading edge portion of the laminated film cannot be temporarily adhered to the surface of the base plate, under heat and pressure, by the thin film temporary adhering member instantaneously but needs to be maintained under heat and pressure by the temporary adhering member for a prescribed length of time. For that reason, the period of adhering of the laminated film to the base plate is increased due to the temporary adhering. This is yet another problem. Since the thin film adhering member includes not only a mechanism for suctioning the leading edge portion of the laminated film but also the heater, the construction of the thin film adhering apparatus is more complicated due to that of the temporary adhering member. This is yet another problem.